1. Field of the Invention
The present invention is related to an innovative method and a medium for long-term preservation of platelets, red blood cells (RBC), and other non-nucleus cells in a powdered form. Also provided is a platelet-containing composition, prepared by contacting platelets with the medium for preserving.
2. Description of the Prior Art
Platelets are the smallest circulating blood cells in human body playing the role more than a plug to stop vascular leaks, but also having the ability to release a variety of growth factors that modulate cell growth and promote tissue repair and regeneration.
Since 1960's, scientists have focused attention upon methods of storing platelets in vitro, cumulating with at present an in solution storage capability in a medium of citrated plasma up to 5 days at 22□ at stable pH levels (pH 6.8-7.2) being achieved. In vitro studies further suggest that storage conveyance technology for platelet concentrates (PCs) is in solution within containers composed of polyolefin for periods up to 5-7 days at room temperature. However, the risk of bacterial contamination in solutions stored at room temperature for this period limits the time during which platelets may be used for transfusion to five days, as established by the FDA.
With blood shortages being increasingly common as the donor base declines and extensive restrictions on blood donation disqualify many donors, red blood cell (RBC) and platelet substitution have long been anticipated as an alternative to standard transfusions.
In particular, a variety of injuries involving excessive bleeding specifically call for the transfusion of platelets. However, due to the degradation of platelet functionality as a consequence current storage technologies, an effective approach for a long-term storage of functionally active platelets has never been succeeded up until now.
Maintaining the normal platelet form in terms of their functional and structural integrity throughout the entire preservation process is of critical importance to ensure their potency when called upon. This is reflected in a preservation process that does not alter the platelet's shape, prevents the excretion of activators and wards off aggregate during preparation and stabilization of the concentration. At molecular level, the ideal preservation process should also retain the glycoprotein Ib/IX, which serves as the receptor for von Willebrand factor, or glycoprotein IIb/IIIa, which serves as the receptor for fibrinogen. It's furthermore necessary for certain metabolic pathways which release messenger substance in response to the bindings of ligands to receptors and which set in motion physiological processes, for example secretion from α-granule, to remain intact. In order to fulfil their normal coagulation function after reconstitution, however, it is crucial to maintain normal intact membranes, functional enzymes, and preserve aggregation, release and phagocytosis responses, i.e. produce viable platelets.
Lyophilization of platelets provides an alternative preserving method that fulfils the above criteria. Lyophilized platelets can be stored at room temperature for an extended period of time and easily reconstituted for use. Moreover, lyophilization improves both shelf life and transportation logistics. In addition, creative approaches to RBC membrane modification, such as the enzymatic cleavage of ABH glycoproteins, may lead to a universal RBC. Advances in the understanding of platelet membrane behaviour at low temperatures may lead to extended platelet storage at refrigerator temperatures.
In view of the drawbacks of current preservation technologies, an effective new method and medium that extends both the quality and duration of the preservation of platelets, RBC and other non-nucleus cells are desperately needed. Therefore, the present invention that facilitates lyophilization of platelets will be a useful alternative for selected clinical applications and will lessen the dependence on marginally adequate blood supplies.